You've been hearing for decades about how a healthy diet is one that
lowers your intake of saturated fats and replaces them with "healthy"
unsaturated oils. This, you have been told, will lower your cholesterol
and your risk of having a heart attack.
What you probably didn't hear is that a study published in the British
Medical Journal (BMJ) February of this past year found that though the
first claim is true--swapping out saturated fats for vegetable oils will
lower your cholesterol--if the oil you use instead of saturated fat is
full of omega-6 fatty acid, like safflower oil or corn oil, the second
claim is completely false.
The study found that when men who had already had a heart attack
replaced saturated fats with safflower oil and ate margarine made with
safflower oil they significantly raised the risk that they would die of a
heart attack, stroke or, in fact, any cause of death, over the next
five years.
How significantly was that risk raised? The study states: "
Among the
control and intervention groups combined, an increase of 5% of food
energy from unspecified PUFA [polyunsaturated fatty acids] predicted
about 30% higher risk of cardiovascular death and all cause mortality.
A reduction in SFA [saturated fat] and increase in the PUFA:SFA ratio
were also associated with increased risks of all cause and
cardiovascular mortality." In short, the more they replaced saturated
fat with "healthy" polyunsaturated oil the more likely they were to die.
I was only made aware of this study last week, when the Canadian Medical
Association Journal (CMAJ) published an opinion piece questioning
whether the government should be putting "heart healthy" labels on corn
oil and other polyunsaturated fats. (Details
HERE.) They cited the February BMJ study in their write-up.
What doesn't come across in the small amount of press the CMAJ article
got is something that makes the BMJ study even more significant: The
data that this finding was based on was 40 years old. It was collected
during the Sydney Diet Heart Study, a randomized controlled trial
conducted in 1966-73.
This was one of the many landmark interventional studies whose result
was used to convince doctors that replacing saturated fats with
polyunsaturated fats would lower cholesterol and, by implication,
prevent heart disease.
But while the authors of the original study published the finding that
the polyunsaturated fats would lower both cholesterol and triglycerides,
they did not look to see whether lowering cholesterol with this
intervention actually helped prevent heart-related deaths.
They eventually admitted in a study published in 1978--a full 5 years
after they began to publish their results--that there was a higher "all
cause mortality" in the group eating the safflower oil, but they did not
look at whether these deaths were from cardiovascular-related causes.
This was a surprising omission, given the point of the dietary
intervention--to lower cholesterol in order to prevent heart attacks.
So it was only in the last few years that a new group of researchers
were able to go back to the original study's raw data and take another
look at it. When they did so, they discovered what they term "previously
missing data." This "missing data" was the data that led to the
conclusion that there was a 30% greater risk of cardiovascular death
among the people in the study who ate the cholesterol-lowering oil.
 |
| Where the Smoking Gun Was Hiding |
Getting at this missing data was not a trivial process. The original
study data had been stored on 9-track tape--the kind you can see at
left--which used to be used by IBM 360 series mainframe computers. There
are only a very few data recovery specialists around who can still read
these kinds of tapes.
Once they recovered the data, the researchers did a very careful
analysis, teasing out other factors that might have affected the death
rate and, most significantly, analyzing whether the transfat associated
with the margarine the test subjects ate might have explained the higher
death rate. They conclude it did not.
They also point out that this re-analysis of the data echoes what was
found in two other re-analyses of 1960-70s era cholesterol/heart diet
trials: Linoleic acid, with its high proportion of Omega-6 fatty acid
and complete lack of Omega-3 fatty acid is really toxic stuff.
You can read the whole BMJ study here:
Use
of dietary linoleic acid for secondary prevention of coronary heart
disease and death: evaluation of recovered data from the Sydney Diet
Heart Study and updated meta-analysis.
Omega-6 Fatty Acids Promote Inflammation
The researchers believe that the reason that the polyunsaturated oils
used in these cholesterol-lowering diets were so toxic was because the
vegetable oils used were very high in Linoleic Acid, an Omega-6 fatty
acid, and devoid of the countervailing Omega-3 fatty acids you need to
consume to keep Omega-6 fatty acids from promoting inflammation.
So, okay. Safflower oil is now out of your diet. But it turns out that
safflower oil is not the only common vegetable oil that is rich in
linoleic oil. Corn oil is very high in it, too. You can see a complete
list of oils sorted by their percentage of Linoleic acid
HERE.
Finally, though health nuts who still fear that eating saturated fat
will kill them will tell you that canola oil and flaxseed oil are
healthier alternatives, neither of these oils has been a part of the
human diet for any significant period of time the way animal and dairy
fats have been.
Canola oil does contain Omega-3 fatty acids, but the process used to
take away its rank smell and keep it from going rancid is likely to
damage them. Damaged Omega-3 oils is not healthy. Flaxseed oil is the
recently renamed stuff we used to call linseed oil and use for mixing up
oil based paint--which it often tastes like. It's safe to eat if you
keep it refrigerated and don't let it go rancid, but since it is not a
traditional food, I would suggest eating it in small quantities.
Palm oil is another fat that has recently made its way into our food
system, as manufacturers are using it as a replacement for the
hydrogenated oils full of transfat. But while there may be health
benefits from consuming the palm oil eaten in traditional societies, the
industrially processed palm oil that is appearing on supermarket
shelves is very different stuff and may very well be harboring
transfat-like molecules that escape the FDA labeling requirements. And
besides that, it often tastes--and refuses to melt--suspiciously like
lipgloss. Treat it with caution.
Stick to the traditional healthy vegetable oils and fats like olive,
coconut , and melted butter, and you are more likely to actually improve
your health.
source: http://diabetesupdate.blogspot.com/2013/11/study-lower-your-cholesterol-and-raise.html
